Refresh Now and Then

DRAM stores information in electric charge. Because DRAM cells lose stored charge over time due to leakage, they have to be \"Refreshed\" in a periodic manner to retain the stored information. This refresh activity is a source of increased energy consumption as the DRAM density grows. It also incurs non-trivial performance loss due to the unavailability of memory arrays during refresh. This paper first presents a comprehensive measurement based characterization study of the cell-level data retention behavior of modern low-power DRAM chips. 99.7% of the cells could retain the stored information for longer than 1 second at a high temperature.